Control device



Dec. 22, 1959 J. L. HARRIS CONTROL DEVICE Original Filed July 28. 1949 INVENTOR. KM

United States Patent CONTROL DEVICE John L. Harris, Whitefish Bay, Wis.

Original application July 28, 1949, Serial No. 107,219. Divided and this application June 24, 1954, Serial No. 439,013

3 Claims. (Cl. 74125') This application is a division of my copending application Serial No. 107,219, filed July 28, 1949, now abancloned.

This invention relates to intermittent drive mechanisms for motor driven timers.

The primary object of the invention is to provide an intermittent drive mechanism for a timer cam shaft which serves to hold the shaft in each position and which causes the holding force to disappear for the instant the shaft is moved from one position to the next.

Other objects will appear from the following description and appended claims.

For a full disclosure of the invention, reference is made to the accompanying drawing which is a front elevation of one form of the invention.

In this drawing, the gear 38 is driven by a timer motor (not shown). This gear drives a gear 85 which, in turn, drives a cam 86. This cam operates a cam follower 87 which is held in place by a pivot pin 88 mounted on the back member 7. The cam follower is provided with inwardly extending ears having slotted holes 89 through which the pin 88 extends. The cam follower 87 is also provided with a stop section 90 which is formed to fit into notches 91 in ratchet wheel 92 which drives the cam shaft. The cam follower 87 is also pivotally attached to a pawl 93 which engages the ratchet wheel and which is biased by means of a spring 94. It will be apparent that the spring 94 pulls the pawl 93 into the ratchet wheel and also pulls the cam follower 87 into engagement with the cam 85 and the ratchet wheel 92. In operation, the cam 86 is driven in a clockwise direction and gradually rotates the cam follower about its stop end 90 which bears against the ratchet wheel. This holds the ratchet wheel and cam shaft stationary in a positive position. At this time the pawl moves backwards to engage the next notch in the ratchet wheel. When the cam follower drops off the cam, the spring 94 is free to pull the pawl 93 downwardly and thus rotate the ratchet wheel one notch. During the drop off movement of the cam follower, the reaction of the cam follower at its stop end is zero and thus there is no reactive force available at the stop end 90 of the cam follower. Thus the holding force of the cam follower on the ratchet wheel disappears during the turning movement of the ratchet wheel. However, when the cam follower strikes the bottom of the cam this reactive force immediately reappears and holds the cam shaft stationary.

Inasmuch as many vairations in form may be made without departing from the spirit and scope of the invention, it is desired to be limited only by the appended claims.

What is claimed is:

1. In a motor driven timer, the combination of, a control shaft, a ratchet wheel, a motor driven cam, a cam follower having one portion engaging said ratchet wheel for holding the same, said cam follower having another portion engaging said motor driven cam, lost motion means supporting the cam follower, a pawl arranged to engage the ratchet wheel at a point spaced from the cam follower, means for attaching the pawl to the cam follower and arranged to permit relative movement therebetween, and means for biasing the cam follower against the cam and ratchet wheel.

2. In a motor driven timer, the combination of, a control shaft, a ratchet wheel, a motor driven cam arranged for rotation and having an abrupt drop-off, a floating cam follower having one portion engaging the ratchet wheel and another portion engaging the cam, means associated with the cam follower arranged to restrain motion thereof relative to the direction of rotation of the cam at the point of engagement of the cam follower therewith, means for applying a biasing force to the cam follower between its points of engagement with the cam and ratchet wheel, whereby the holding force of the cam follower on the ratchet wheel is a function of the force of the cam follower against the cam, and a pawl operated by the cam follower for rotating the ratchet wheel.

3. In a motor driven timer, the combination of, a control shaft, ratchet wheel means on the shaft for rotating and holding the shaft from rotation, a motor driven cam having an abrupt drop-01f, a floating cam follower having one portion engaging the ratchet wheel means and another portion engaging the cam, means associated with the cam follower for restraining motion of the cam follower in a direction substantially tangential to its point of engagement with the ratchet wheel means, means for applying a biasing force to the cam follower between its points of engagement with the cam and ratchet wheel means whereby the holding force of the cam follower on the ratchet wheel means is a function of the force of the cam follower against the cam, and a pawl operated by the cam follower for rotating the ratchet wheel means when the cam followers drops off the cam.

References Cited in the file of this patent UNITED STATES PATENTS Re. 13,247 Freeman May, 30, 1911 574,223 Scribner Dec. 29, 1896 2,060,603 Ball Nov. 10, 1936 2,208,831 Basset July 23, 1940 2,214,534 Maxwell Sept. 10, 1940 2,216,597 Minneci Oct. 1, 1940 2,469,341 Pearson May 3, 1949 2,834,249 May May 13, 1958 

